In plasma processing, plasmas create ionized and/or energetically excited species for interaction with workpieces that may be, for example, semiconductor wafers. To create and/or maintain a plasma, one or more radio frequency (RF) and/or microwave generators typically generate oscillating electric and/or magnetic fields. In some wafer processing systems, a plasma is generated in the same location as one or more wafers being processed; in other cases, a plasma is generated in one location and moves to another location where the wafer(s) are processed. The plasmas produced often contain highly energetic and/or corrosive species and/or highly energetic electrons, such that the equipment that produces them sometimes degrades from contact with the energetic species and/or electrons. For example, materials that are exposed to highly energetic species may be etched and/or sputtered, generating etched and/or sputtered material that can move about, and can react or deposit on various surfaces.